SPARC and neoplasm: Paradoxically, the expression of cell cycle inhibitors p21CIP/WAF1 and p27KIP1 significantly and progressively decreased in SPARC-deficient compared to SPARC-proficient urothelial lesions; a finding that phenocopies their perturbed expression in human urothelial cancer [55–65] and further supports the tumor suppressor effect of SPARC in part through inhibition of cell cycle progression at G1/S.